The present invention relates in general to autoreverse cassette tape mechanisms and more specifically to detection of a condition potentially leading to a jamming of tape at the pinch roller and/or capstan.
An autoreverse cassette tape player reproduces signals from both sides of a cassette without having to remove the tape from the player in order to turn it over. In such a player, the drive mechanism must be able to drive the tape in either direction. A magnetic head for picking up signals from the tape typically moves up and down to be located over the portion of the tape having the recorded signals, or separate pick-ups may be provided.
During playback, cassette tape is drawn from a supply reel past the magnetic head to the take-up reel using a capstan and pinch roller to draw the tape at a constant speed. The take-up reel is driven in the proper direction to store tape that has been drawn past the magnetic head. When the autoreverse mechanism changes direction, the supply and take-up reels are reversed and a separate capstan and pinch roller pair on the opposite side of the magnetic head assumes the job of drawing the tape past the head.
A well known problem referred to as "tape eating" can occur during tape playback whenever the tape becomes jammed in the vicinity of the capstan and pinch roller. For example, tape may stick to the rotating capstan and become wound on the capstan. Both the cassette tape and the cassette mechanism can become damaged by jamming. Further damage can occur when attempting to eject a jammed tape. The mechanism may even become so jammed that the tape cannot be ejected.
During normal tape playback in an autoreverse mechanism, tape direction is automatically reversed when the end of one side of the tape is reached. The end of tape condition is sensed when the take-up reel stops rotating in the take-up direction. A tape direction change cycle typically takes about 2 seconds to be completed.
During a tape-eating condition, the take-up reel stops moving just as though the end of the tape had been reached. Thus, a tape-eating condition also results in a tape direction change cycle. However, during a tape-eating condition the pinch roller and capstan continue eating tape, which forces the supply reel to keep supplying tape for the duration of the tape direction change cycle. During the 2 seconds it takes for the mechanism to change direction, as much as 2 inches of tape may be eaten by the pinch roller and capstan, thereby not permitting the tape mechanism to recover its normal operating condition after the direction change.